{"id":77842,"date":"2024-10-16T11:12:16","date_gmt":"2024-10-16T03:12:16","guid":{"rendered":"https:\/\/server.hk\/cnblog\/77842\/"},"modified":"2024-10-16T11:12:16","modified_gmt":"2024-10-16T03:12:16","slug":"mysql%e6%8c%87%e4%bb%a4-case%ef%bc%88%e6%a2%9d%e4%bb%b6%e8%aa%9e%e5%8f%a5%ef%bc%89","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/77842\/","title":{"rendered":"MySQL\u6307\u4ee4: CASE\uff08\u689d\u4ef6\u8a9e\u53e5\uff09"},"content":{"rendered":"<h1 id=\"mysql%e6%8c%87%e4%bb%a4-case%ef%bc%88%e6%a2%9d%e4%bb%b6%e8%aa%9e%e5%8f%a5%ef%bc%89-hjsJzDYYVt\">MySQL\u6307\u4ee4: CASE\uff08\u689d\u4ef6\u8a9e\u53e5\uff09<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cMySQL\u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u95dc\u806f\u5f0f\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u3002\u5b83\u63d0\u4f9b\u4e86\u591a\u7a2e\u529f\u80fd\u4f86\u8655\u7406\u548c\u67e5\u8a62\u8cc7\u6599\uff0c\u5176\u4e2d\u4e4b\u4e00\u5c31\u662fCASE\u8a9e\u53e5\u3002CASE\u8a9e\u53e5\u662f\u4e00\u7a2e\u689d\u4ef6\u8a9e\u53e5\uff0c\u5141\u8a31\u7528\u6236\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u8fd4\u56de\u4e0d\u540c\u7684\u7d50\u679c\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0eMySQL\u4e2d\u7684CASE\u8a9e\u53e5\uff0c\u5305\u62ec\u5176\u8a9e\u6cd5\u3001\u4f7f\u7528\u60c5\u5883\u53ca\u7bc4\u4f8b\u3002<\/p>\n<h2 id=\"case%e8%aa%9e%e5%8f%a5%e7%9a%84%e5%9f%ba%e6%9c%ac%e8%aa%9e%e6%b3%95-hjsJzDYYVt\">CASE\u8a9e\u53e5\u7684\u57fa\u672c\u8a9e\u6cd5<\/h2>\n<p>CASE\u8a9e\u53e5\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>\nCASE\n    WHEN condition1 THEN result1\n    WHEN condition2 THEN result2\n    ...\n    ELSE resultN\nEND\n<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c<code>condition<\/code>\u662f\u8981\u8a55\u4f30\u7684\u689d\u4ef6\uff0c\u800c<code>result<\/code>\u662f\u7576\u689d\u4ef6\u70ba\u771f\u6642\u8fd4\u56de\u7684\u503c\u3002\u5982\u679c\u6240\u6709\u689d\u4ef6\u90fd\u4e0d\u6eff\u8db3\uff0c\u5247\u8fd4\u56de<code>ELSE<\/code>\u5f8c\u7684\u7d50\u679c\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8case%e8%aa%9e%e5%8f%a5%e7%9a%84%e6%83%85%e5%a2%83-hjsJzDYYVt\">\u4f7f\u7528CASE\u8a9e\u53e5\u7684\u60c5\u5883<\/h2>\n<p>CASE\u8a9e\u53e5\u901a\u5e38\u7528\u65bc\u4ee5\u4e0b\u60c5\u5883\uff1a<\/p>\n<ul>\n<li><strong>\u6578\u64da\u5206\u985e\uff1a<\/strong>\u6839\u64da\u67d0\u4e9b\u689d\u4ef6\u5c07\u6578\u64da\u5206\u7d44\u6216\u5206\u985e\u3002<\/li>\n<li><strong>\u8a08\u7b97\u884d\u751f\u6b04\u4f4d\uff1a<\/strong>\u6839\u64da\u4e0d\u540c\u7684\u689d\u4ef6\u8a08\u7b97\u65b0\u7684\u6b04\u4f4d\u503c\u3002<\/li>\n<li><strong>\u5831\u544a\u751f\u6210\uff1a<\/strong>\u5728\u751f\u6210\u5831\u544a\u6642\u6839\u64da\u4e0d\u540c\u7684\u689d\u4ef6\u986f\u793a\u4e0d\u540c\u7684\u7d50\u679c\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%af%84%e4%be%8b%ef%bc%9a%e4%bd%bf%e7%94%a8case%e8%aa%9e%e5%8f%a5-hjsJzDYYVt\">\u7bc4\u4f8b\uff1a\u4f7f\u7528CASE\u8a9e\u53e5<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u4f7f\u7528CASE\u8a9e\u53e5\u7684\u7bc4\u4f8b\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba<code>employees<\/code>\u7684\u8868\u683c\uff0c\u5305\u542b\u54e1\u5de5\u7684\u59d3\u540d\u548c\u85aa\u6c34\u3002\u6211\u5011\u5e0c\u671b\u6839\u64da\u85aa\u6c34\u7684\u7bc4\u570d\u4f86\u5206\u985e\u54e1\u5de5\u7684\u85aa\u6c34\u7b49\u7d1a\u3002<\/p>\n<pre><code>\nSELECT name,\n       salary,\n       CASE\n           WHEN salary &lt; 30000 THEN &#039;\u4f4e\u85aa&#039;\n           WHEN salary BETWEEN 30000 AND 60000 THEN &#039;\u4e2d\u85aa&#039;\n           ELSE &#039;\u9ad8\u85aa&#039;\n       END AS salary_grade\nFROM employees;\n<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u6211\u5011\u6839\u64da\u85aa\u6c34\u7684\u4e0d\u540c\u7bc4\u570d\u70ba\u6bcf\u4f4d\u54e1\u5de5\u5206\u914d\u4e86\u4e00\u500b\u85aa\u6c34\u7b49\u7d1a\u3002\u9019\u6a23\u7684\u67e5\u8a62\u53ef\u4ee5\u5e6b\u52a9\u7ba1\u7406\u5c64\u5feb\u901f\u4e86\u89e3\u54e1\u5de5\u7684\u85aa\u6c34\u5206\u4f48\u60c5\u6cc1\u3002<\/p>\n<h2 id=\"case%e8%aa%9e%e5%8f%a5%e7%9a%84%e5%b5%8c%e5%a5%97%e4%bd%bf%e7%94%a8-hjsJzDYYVt\">CASE\u8a9e\u53e5\u7684\u5d4c\u5957\u4f7f\u7528<\/h2>\n<p>CASE\u8a9e\u53e5\u4e5f\u53ef\u4ee5\u5d4c\u5957\u4f7f\u7528\uff0c\u4ee5\u8655\u7406\u66f4\u8907\u96dc\u7684\u908f\u8f2f\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u60f3\u8981\u6839\u64da\u54e1\u5de5\u7684\u85aa\u6c34\u548c\u5e74\u9f61\u4f86\u9032\u4e00\u6b65\u5206\u985e\u85aa\u6c34\u7b49\u7d1a\uff1a<\/p>\n<pre><code>\nSELECT name,\n       salary,\n       age,\n       CASE\n           WHEN salary &lt; 30000 THEN \n               CASE \n                   WHEN age &lt; 30 THEN &#039;\u5e74\u8f15\u4f4e\u85aa&#039;\n                   ELSE &#039;\u6210\u719f\u4f4e\u85aa&#039;\n               END\n           WHEN salary BETWEEN 30000 AND 60000 THEN &#039;\u4e2d\u85aa&#039;\n           ELSE &#039;\u9ad8\u85aa&#039;\n       END AS salary_grade\nFROM employees;\n<\/code><\/pre>\n<p>\u5728\u9019\u500b\u7bc4\u4f8b\u4e2d\uff0c\u6211\u5011\u4e0d\u50c5\u8003\u616e\u4e86\u85aa\u6c34\uff0c\u9084\u8003\u616e\u4e86\u5e74\u9f61\uff0c\u5f9e\u800c\u63d0\u4f9b\u4e86\u66f4\u7d30\u7dfb\u7684\u5206\u985e\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-hjsJzDYYVt\">\u7e3d\u7d50<\/h2>\n<p>MySQL\u4e2d\u7684CASE\u8a9e\u53e5\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u6839\u64da\u4e0d\u540c\u7684\u689d\u4ef6\u8fd4\u56de\u4e0d\u540c\u7684\u7d50\u679c\u3002\u5b83\u4e0d\u50c5\u53ef\u4ee5\u7528\u65bc\u6578\u64da\u5206\u985e\uff0c\u9084\u53ef\u4ee5\u7528\u65bc\u8a08\u7b97\u884d\u751f\u6b04\u4f4d\u548c\u751f\u6210\u5831\u544a\u3002\u901a\u904e\u9748\u6d3b\u904b\u7528CASE\u8a9e\u53e5\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u66f4\u6709\u6548\u5730\u8655\u7406\u548c\u5206\u6790\u6578\u64da\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u7ba1\u7406\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u4f86\u904b\u884c\u60a8\u7684MySQL\u8cc7\u6599\u5eab\uff0c\u4eab\u53d7\u7a69\u5b9a\u548c\u5b89\u5168\u7684\u670d\u52d9\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3MySQL\u4e2d\u7684CASE\u6307\u4ee4\uff0c\u5b78\u7fd2\u5982\u4f55\u4f7f\u7528\u689d\u4ef6\u8a9e\u53e5\u9032\u884c\u6578\u64da\u67e5\u8a62\u548c\u8655\u7406\uff0c\u63d0\u5347\u6578\u64da\u5eab\u64cd\u4f5c\u6548\u7387\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-77842","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/77842","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=77842"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/77842\/revisions"}],"predecessor-version":[{"id":77843,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/77842\/revisions\/77843"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=77842"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=77842"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=77842"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}